1 Correlating catalytic methanol oxidation with the structure and oxidation state of size- 1 selected Pt nanoparticles 2 Lindsay R. Merte, 1 Mahdi Ahmadi, 1 Farzad Behafarid, 1 Luis K. Ono, 1 Estephania Lira, 1 3 Jeronimo Matos, 1 Long Li, 2 Judith C. Yang 2 and Beatriz Roldan Cuenya 1,* 4 5 1 Department of Physics, University of Central Florida, Orlando, Florida 32816, United States 6 2 Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, 7 Pennsylvania 15261, United States 8 * Corresponding author: [email protected]9 Keywords: platinum; methanol oxidation; operando; XAS; EXAFS; alumina; nanoparticle; size 10 selected 11 12 Abstract 13 We have investigated the structure and chemical state of size-selected platinum nanoparticles 14 (NPs) prepared by micelle encapsulation and supported on γ-Al 2 O 3 during the oxidation of 15 methanol under oxygen-rich reaction conditions following both oxidative and reductive 16 pretreatments. X-ray absorption near-edge structure (XANES) and extended x-ray absorption 17 fine-structure (EXAFS) spectroscopy measurements reveal that in both cases, the catalyst is 18 substantially oxidized under reaction conditions at room temperature and becomes partially 19 reduced when the reactor temperature is raised to 50°C. Reactivity tests show that at low 20 temperatures the pre-oxidized catalyst, where a larger degree of oxidation was observed, is more 21 active than the pre-reduced catalyst. We conclude that the differences in reactivity can be linked 22 to the formation and stabilization of distinct active oxide species during the pretreatment. 23 24
27
Embed
2 selected Pt nanoparticles - UCF Physicsroldan/publications/2013_Merte_ACSCatal.pdf · 2 selected Pt nanoparticles ... 22 active than the pre-reduced catalyst. ... The reactor used
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
Correlating catalytic methanol oxidation with the structure and oxidation state of size-1
selected Pt nanoparticles 2
Lindsay R. Merte,1 Mahdi Ahmadi,1 Farzad Behafarid,1 Luis K. Ono,1 Estephania Lira,1 3
Jeronimo Matos,1 Long Li,2 Judith C. Yang2 and Beatriz Roldan Cuenya1,* 4
5
1 Department of Physics, University of Central Florida, Orlando, Florida 32816, United States 6
2 Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, 7
Table 1. Pt L3 EXAFS fit parameters for the Pt/γ-Al2O3 catalyst in the as-prepared, reduced and 4
oxidized states as well as under methanol combustion conditions following reducing and 5
oxidizing pretreatments. Fit parameters for a Pt foil are shown for reference. nPt-Pt, nPt-O(1) and nPt-6
O(2) are coordination numbers and dPt-Pt, dPt-O(1) and dPt-O(2) are bond lengths for the three distinct 7
scattering species. 8
9
10
11
17
1
2
Figure 1. (a) AFM image of the Pt-loaded PS-b-P2VP micellar precursor used to prepare the 3
Pt/γ-Al2O3 catalyst used in this study. Micelles were dip-coated onto an SiO2/Si(111) wafer for 4
imaging; polymer ligands were not removed. (b) Pt-4d XPS spectrum of the as-prepared 5
(calcined) Pt/γ-Al2O3 catalyst. Binding energies expected for Pt, PtO and PtO2 are indicated. (c) 6
HAADF-STEM image of the Pt/γ-Al2O3 catalyst after ligand removal and after operando XAFS 7
measurements. (d) Particle size distribution extracted from HAADF-STEM measurements. 8
9
10
18
1
2
3
Figure 2. Reactivity of the undiluted Pt/γ-Al2O3 catalyst for methanol oxidation following (a) 4
reductive (240 °C in 50% H2 for 30 mins.) and (b) oxidative (240 °C in 70% O2 for 30 mins.) 5
pretreatments. Conversion refers to the molar fraction of methanol in the feed converted to a 6
particular product. Plotted points are individual measurements and solid curves are guides to the 7
eye. Carbon dioxide (CO2) and methyl formate (CHOOCH3) were the only products detected in 8
significant quantities. All data shown correspond to steady-state reaction conditions at each 9
given temperature. 10
11
19
1
2
Figure 3. Reactivity of the diluted Pt/γ-Al2O3 catalyst for methanol oxidation. Reactivity 3
following (a) reductive, and (b) oxidative pretreatments, measured with increasing temperature. 4
(c) Reactivity following reductive and oxidative pretreatments, measured with decreasing 5
temperature following the measurements shown in (a) and (b). 6
7
20
1
Figure 4. Pt-L3 XANES spectra of a Pt/γ-Al2O3 catalyst acquired following oxidative and 2
reductive pretreatments and under methanol oxidation conditions after these pretreatments. (a) 3
Comparison of spectra acquired under reaction conditions at room temperature beginning in the 4
reduced state (treated in H2 at 240°C) and an oxidized state (treated in O2 at 240°C), 5
respectively. XANES spectra acquired of the as-prepared (oxidized) catalyst and of a bulk Pt foil 6
are shown for reference. (b) Comparison of spectra acquired under reaction conditions at 7
different temperatures. 8
21
1
Figure 5. Fourier-transformed k2-weighted EXAFS spectra of the Pt/γ-Al2O3 catalyst after 2
reduction, oxidation and under MeOH oxidation reaction conditions following the two 3
pretreatments leading to the oxidation and reduction of the catalysts. Shown also are first-shell 4
fits to the experimental data using a combination of three scattering components, as described in 5
the text. A Hanning window from 2.5 to 13 Å-1 with Δk=1 Å-1 was used to compute the Fourier 6
transforms. The data are vertically displaced for clarity. 7
8
22
1
2
Figure 6. (a) Fourier –transformed (k=2.5-15.5 Å-1) EXAFS spectrum of the initially-reduced 3
catalyst measured at 25°C in MeOH+O2. The fitted spectrum as well as the magnitudes of the 4
three contributing scattering components corresponding to metallic Pt, a Pt-O(1) bond at ~2.0 Å, 5
and Pt-O(2) at ~2.5 Å are also shown. (b) Inverse-Fourier-transformed (R=1.2-3.2 Å) EXAFS 6
spectrum corresponding to that in (a). 7
8
23
1
2
3
Figure 7. Coordination numbers of three different Pt species extracted from first-shell analysis 4
of EXAFS spectra. The sample was exposed to two different pre-treatments under reductive 5
(left) and oxidative (right) conditions. Spectra were acquired under the conditions indicated, in 6
order from left to right. 7
8
9
10
24
1
2
3
4
5
6
TOC figure 7
8
9
10
11
12
25
References 1
2
3
(1) Lefferts, L.; van Ommen, J. G.; Ross, J. R. H. Appl. Catal. 1986, 23, 385. 4 (2) Nagy, A.; Mestl, G. Appl. Catal. A 1999, 188, 337. 5 (3) Guerreiro, E. D.; Gorriz, O. F.; Larsen, G.; Arrúa, L. A. Appl. Catal. A 2000, 204, 33. 6 (4) Wittstock, a.; Zielasek, V.; Biener, J.; Friend, C. M.; Bäumer, M. Science 2010, 327, 319. 7 (5) Spivey, J. J. Ind. Eng. Chem. Res. 1987, 26, 2165. 8 (6) Sharma, R. K.; Zhou, B.; Tong, S.; Chuane, K. T.; Tg, A. Ind. Eng. Chem. Res. 1995, 34, 9 4310. 10 (7) Gandhi, H. S.; Graham, G. W.; McCabe, R. W. J. Catal. 2003, 216, 433. 11 (8) Tatibouët, J. M. Appl. Catal. A 1997, 148, 213. 12 (9) Iwasita, T. Electrochim. Acta 2002, 47, 3663. 13 (10) Lamy, C.; Lima, A.; LeRhun, V.; Delime, F.; Coutanceau, C.; Léger, J.‐M. J. Power Sources 14 2002, 105. 15 (11) Mallat, T.; Baiker, A. Chem. Rev. 2004, 104, 3037. 16 (12) Markusse, A. P.; Kuster, B. F. M.; Koningsberger, D.; Marin, G. B. Catal. Lett. 1998, 55, 17 141. 18 (13) Nicoletti, J. W.; Whitesides, G. M. J. Phys. Chem. 1989, 93, 759. 19 (14) Ackermann, M. D.; Pedersen, T. M.; Hendriksen, B. L. M.; Robach, O.; Bobaru, S. C.; 20 Popa, I.; Quiros, C.; Kim, H.; Hammer, B.; Ferrer, S.; Frenken, J. W. M. Phys. Rev. Lett. 2005, 95, 255505. 21 (15) Hendriksen, B. L. M.; Frenken, J. W. M. Phys. Rev. Lett. 2002, 89, 2. 22 (16) Li, W.‐X. J. Phys.: Condens. Matter 2008, 20, 184022. 23 (17) Mallens, E. P. J.; Hoebink, J. H. B. J.; Marin, G. B. Catal. Lett. 1995, 33, 291. 24 (18) Gao, F.; Wang, Y.; Cai, Y.; Goodman, D. W. J. Phys. Chem. C 2009, 113, 174. 25 (19) McClure, S. M.; Goodman, D. W. Chem. Phys. Lett. 2009, 469, 1. 26 (20) Alayon, E. M. C.; Singh, J.; Nachtegaal, M.; Harfouche, M.; van Bokhoven, J. A. J. Catal. 27 2009, 263, 228. 28 (21) Singh, J.; van Bokhoven, J. A. Catal Today 2010, 155, 199. 29 (22) Croy, J. R.; Mostafa, S.; Heinrich, H.; Roldan Cuenya, B. Catal. Lett. 2009, 131, 21. 30 (23) Mostafa, S.; Behafarid, F.; Croy, J. R.; Ono, L. K.; Li, L.; Yang, J. C.; Frenkel, A. I.; Roldan 31 Cuenya, B. J. Am. Chem. Soc. 2010, 132, 15714. 32 (24) Paredis, K.; Ono, L. K.; Mostafa, S.; Li, L.; Zhang, Z.; Yang, J. C.; Barrio, L.; Frenkel, A. I.; 33 Roldan Cuenya, B. J. Am. Chem. Soc. 2011, 133, 6728. 34 (25) Singh, J.; Nachtegaal, M.; Alayon, E. M. C.; Stotzel, J.; van Bokhoven, J. A. Chemcatchem 35 2010, 2, 653. 36 (26) Roldan Cuenya, B. Thin Solid Films 2010, 518, 3127. 37 (27) Matos, J.; Ono, L. K.; Behafarid, F.; Croy, J. R.; Mostafa, S.; DeLaRiva, A. T.; Datye, A. K.; 38 Frenkel, A. I.; Roldan Cuenya, B. Phys. Chem. Chem. Phys. 2012, 14, 11457. 39 (28) Ravel, B.; Newville, M. J. Synchrotron Rad. 2005, 12, 537. 40 (29) Rehr, J. J.; Albers, R. C. Rev. Mod. Phys. 2000, 72, 621. 41 (30) Ankudinov, A. L.; Bouldin, C. E.; Rehr, J. J.; Sims, J.; Hung, H. Phys. Rev. B 2002, 65, 42 104107 43 (31) Croy, J. R.; Mostafa, S.; Liu, J.; Sohn, Y.‐h.; Roldan Cuenya, B. Catal. Lett. 2007, 118, 1. 44 (32) Kästle, G.; Boyen, H.‐G.; Weigl, F.; Lengl, G.; Herzog, T.; Ziemann, P.; Riethmüller, S.; 45 Mayer, O.; Hartmann, C.; Spatz, J. P.; Möller, M.; Ozawa, M.; Banhart, F.; Garnier, M. G.; Oelhafen, P. 46 Adv. Func. Mater. 2003, 13, 853. 47
26
(33) Roldan Cuenya, B.; Baeck, S.‐H.; Jaramillo, T. F.; McFarland, E. W. J. Am. Chem. Soc. 1 2003, 125, 12928. 2 (34) Damyanova, S.; Bueno, J. M. C. Appl. Catal. A:Gen 2003, 253, 135. 3 (35) Roldan Cuenya, B.; Croy, J. R.; Mostafa, S.; Behafarid, F.; Li, L.; Zhang, Z.; Yang, J. C.; 4 Wang, Q.; Frenkel, A. I. J. Am. Chem. Soc. 2010, 132, 8747. 5 (36) Mansour, A. N.; Sayers, D. E.; Cook, J. W.; Short, D. R.; Shannon, R. D.; Katzer, J. R. J. 6 Phys. Chem. 1984, 88, 1778. 7 (37) Friebel, D.; Miller, D. J.; O'Grady, C. P.; Anniyev, T.; Bargar, J.; Bergmann, U.; Ogasawara, 8 H.; Wikfeldt, K. T.; Pettersson, L. G. M.; Nilsson, A. Phys. Chem. Chem. Phys. 2011, 13, 262. 9 (38) Merte, L. R.; Behafarid, F.; Miller, D. J.; Friebel, D.; Cho, S.; Mbuga, F.; Sokaras, D.; 10 Alonso‐Mori, R.; Weng, T.‐C.; Nordlund, D.; Nilsson, A.; Roldan Cuenya, B. ACS Catal. 2012, 2, 2371. 11 (39) Behafarid, F.; Ono, L. K.; Mostafa, S.; Croy, J. R.; Shafai, G.; Hong, S.; Rahman, T. S.; Bare, 12 S.; Roldan Cuenya, B. Phys. Chem. Chem. Phys. 2012, 14, 11766. 13 (40) Lei, Y.; Jelic, J.; Nitsche, L. C.; Meyer, R.; Miller, J. Top. Catal. 2011, 54, 334. 14 (41) Frenkel, A. I.; Yevick, A.; Cooper, C.; Vasic, R. Annu. Rev. Anal. Chem. 2011, 4, 23. 15 (42) Jentys, A. Phys. Chem. Chem. Phys. 1999, 1, 4059. 16 (43) Koningsberger, D. C.; Gates, B. C. Catal. Lett. 1992, 14, 271. 17 (44) Paredis, K.; Ono, L. K.; Behafarid, F.; Zhang, Z.; Yang, J. C.; Frenkel, A. I.; Roldan Cuenya, 18 B. J. Am. Chem. Soc. 2011, 133, 13455. 19 (45) Vaarkamp, M.; Miller, J. T.; Modica, F. S.; Koningsberger, D. C. J. Catal. 1996, 163, 294. 20 (46) Zhang, Y.; Toebes, M. L.; van der Eerden, A.; O'Grady, W. E.; de Jong, K. P.; 21 Koningsberger, D. C. J. Phys. Chem. B 2004, 108, 18509. 22 (47) Mager‐Maury, C.; Bonnard, G.; Chizallet, C.; Sautet, P.; Raybaud, P. Chemcatchem 2012, 23 3, 200. 24 (48) McCabe, R. W.; McCready, D. F. J. Phys. Chem. 1986, 90, 1428. 25 (49) Safonova, O. V.; Tromp, M.; van Bokhoven, J. A.; de Groot, F. M. F.; Evans, J.; Glatzel, P. 26 J. Phys. Chem. B 2006, 110, 16162. 27 (50) Chantaravitoon, P.; Chavadej, S.; Schwank, J. Chem. Eng. J. 2004, 97, 161. 28 (51) McCabe, R. W.; Mitchell, P. J. Appl. Catal. 1986, 27, 83. 29 (52) Gentry, J.; Jones, A.; Walsh, T.; Sheffield, S. J. Chem. Soc., Faraday Trans. I 1980, 76, 30 2084. 31 (53) Lichtenberger, J.; Lee, D.; Iglesia, E. Phys. Chem. Chem. Phys. 2007, 9, 4902. 32 (54) Brewer, T. F.; Abraham, M. A.; Silver, R. G. Ind. Eng. Chem. Res. 1994, 33, 526. 33 (55) Chou, P.; Vannice, M. A. J. Catal. 1987, 105, 342. 34 (56) Xu, Y.; Shelton, W. A.; Schneider, W. F. J. Phys. Chem. B 2006, 110, 16591. 35 (57) Xu, Y.; Shelton, W. A.; Schneider, W. F. J. Phys. Chem. A 2006, 110, 5839. 36 (58) Ono, L. K.; Croy, J. R.; Heinrich, H.; Roldan Cuenya, B. J. Phys. Chem. C 2011, 115, 16856. 37 (59) Mars, P.; van Krevelen, D. W. Chem. Eng. Sci. 1954, 3, 41. 38 (60) Hendriksen, B. L. M.; Ackermann, M. D.; van Rijn, R.; Stoltz, D.; Popa, I.; Balmes, O.; 39 Resta, A.; Wermeille, D.; Felici, R.; Ferrer, S.; Frenken, J. W. M. Nat. Chem. 2010, 2, 730. 40 (61) Endo, M.; Matsumoto, T.; Kubota, J.; Domen, K.; Hirose, C. Surf. Sci. 1999, 441, L931. 41 (62) Gong, X.‐Q.; Liu, Z.‐P.; Raval, R.; Hu, P. J. Am. Chem. Soc. 2004, 126, 8. 42 (63) Reuter, K.; Frenkel, D.; Scheffler, M. Phys. Rev. Lett. 2004, 93. 43 (64) Lashina, E. A.; Slavinskaya, E. M.; Chumakova, N. A.; Stonkus, O. A.; Gulyaev, R. V.; 44 Stadnichenko, A. I.; Chumakov, G. A.; Boronin, A. I.; Demidenko, G. V. Chem. Eng. Sci. 2012, 83, 149. 45 (65) Jensen, R.; Andersen, T.; Nierhoff, A.; Pedersen, T.; Hansen, O.; Dahl, S.; Chorkendorff, I. 46 Phys. Chem. Chem. Phys. 2013, 15, 2698. 47 (66) Schwartz, W. R.; Pfefferle, L. D. J. Phys. Chem. C 2012, 116, 8571. 48
27
(67) Müller, C. A.; Maciejewski, M.; Koeppel, R. A.; Tschan, R.; Baiker, A. J. Phys. Chem. 1996, 1 100, 20006. 2 (68) Seriani, N.; Pompe, W.; Ciacchi, L. C. J. Phys. Chem. B 2006, 110, 14860. 3 (69) Li, N.‐H.; Sun, S.‐G.; Chen, S.‐P. J. Electroanal. Chem. 1997, 430, 57. 4 (70) Hellman, A.; Resta, A.; Martin, N. M.; Gustafson, J.; Trinchero, A.; Carlsson, P. A.; Balmes, 5 O.; Felici, R.; van Rijn, R.; Frenken, J. W. M.; Andersen, J. N.; Lundgren, E.; Grönbeck, H. J. Phys. Chem. 6 Lett. 2012, 3, 678. 7